In the Linux kernel, the following vulnerability has been resolved: audit: fix exe mark UAF in kill_rules() kill_rules() removes mixed AUD

In the Linux kernel, the following vulnerability has been resolved:

audit: fix exe mark UAF in kill_rules()

kill_rules() removes mixed AUDIT_DIR and AUDIT_EXE rules when an audit
tree is pruned. It drops entry->rule.exe before removing the rule from
the RCU-visible filter lists.

After a rule has been installed with AUDIT_ADD_RULE, which requires
CAP_AUDIT_CONTROL, removing the watched directory can race with another
task that is still evaluating the rule. In that case, fsnotify can free
the executable mark before the reader reaches audit_mark_compare(),
causing a use-after-free.

KASAN reports:

 1BUG: KASAN: slab-use-after-free in audit_mark_compare+0x8d/0xa0

Unlink the published rules from the RCU-visible lists and retain them
on tree->rules for cleanup. If any rule has an executable mark, wait for
a single RCU grace period before removing the marks and scheduling the
entries for freeing. Otherwise, call_rcu() already provides the required
deferred freeing without a synchronous wait.